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We do not regulate the pressure directly. we have over time come to use a less powerful steam souurce. We have also experimented with captive steam passing through copper tubing in order to heat the water. this proves to be much slower than expected, so there comes a trade off between heat levels and the total time spent wet. Each application has its advantages.

We do not regulate the pressure directly. we have over time come to use a less powerful steam souurce. We have also experimented with captive steam passing through copper tubing in order to heat the water. this proves to be much slower than expected, so there comes a trade off between heat levels and the total time spent wet. Each application has its advantages.

Thanks for the pics.Do you try to evaluate the resistance of those ribs ? due to the difference in grain it may not be easy.

I wonder how do you deal with the drying and stabilization of the wood after all that humidity. It may take some time.

What amount of drying will you use before ribbing ? do you only look at the dimension change or do you work with somewhat precise wood moisture level ,it may be possible just with temperature and room humidity observation I suppose, but for instance to attain 5.5% one need to dry the air, temperature enough would cause the use of very high temperature, I believe that an industrial air drier is better (allow to work at moderate temperature)

Just curious

Best regards

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Professional of the profession. Foo Foo specialistI wish to add some kind and sensitive phrase but nothing comes to mind.!

Isaac,Sorry to have let a week go by before responding. Your questions got me thinking, and, unfortunately, that is a slow process.

In the past, we have never paid too much attention to the actual stiffnesses of any given ribs. As we have always reused the original ribs, and,since we are in no position alter their strength, measuring the stiffness seemed secondary.

On the other hand, we have always used the inherant stiffness of the wood as our guide in the calulation of pressing cauls. using a couple of blocks clamped to the side of a blank caul, just about where the gaining starts on the ribs, we flex the rib to form an arch. Rather than being scientific about this stressing of the rib, we use our sense of wood to tell us what arc is proper for that rib. The rib should be stressed, but also feel like it could go a bit farther. this arc is traced as a basic pattern for all the ribs. We have tended to dish in the treble ribs a bit more, both because they can take it, and the treble is the zone of the board that simply must have crown to function. So we tend to err on the side of caution.

The drying and stabilization of the wood only takes a day or two. Its odd, but old wood seems to both take on and give off moisture at a very rapid pace. By the end of steaming day, the wood no longer looks wet, but if you handle it, it feels both heavy and cold to the touch. The next day the wood feels lighter, but still cool. the day after that the wood is light in weight and warm to the touch because evaporation has finished.

We have always used the dimensional change in the panel as our guide to when to press on the ribs. We find that 24 hours under the heat is enough time to shrink the board. This is the time of year that we avoided any bellywork because the temp needed to shift the wood is very high.

I would love to have a climate control system. It would allow us to regularize the enviroment we press in and we could ignore the weather. Even with climate controll, we would still run the space at around 100F. We use cow-hide glue, and that is best applied to well warmed pieces of wood, and the heated environment will help dry the board after we clean up the excess glue with water. This is where the woods ability to give off excess water so rapidly comes into play.

Thanks for the interest, I do appreciate it

By the way, I came across an old "Piano Atlas" by Sievers, 1868. Is this an available book, and should I digitize it?

Good Morning,In this piano, I would have to say that the ribs are glued on both during and before the crowning takes place. We used gently dished cauls to do the gluing, so the board came out of the press with a little crown displayed. We also dried the board our beforehand,120F, such that the panel shrank about 6mm across its width. After the gluing, when the moisture returns to the panel, the crown in the long ribs develops. This happens over several days. This morning, the crown on the underside, between the longest ribs, is about 16mm. Between the two top treble ribs we have about 4mm. A good deal of this displayed crown will be lost when the rib ends are glued down to a 90 deg. shelf.

Thank you indeed for posting these pictures, Mr. Hair. Having an interest in the mechanical properties of the soundboard, but not being in the business, I was very interested in seeing the cross section of the grain.

Good evening,Its only part illusion. the grain is far from vertical. Actually much of the wood in this board seems less than ideal. There is a lot of grain runout in the planks. One board has a curve of about 2 inches in the grain from one end to the other.

Perhapse we are just spoiled when it comes to wood selection in America. The German city-states of the 19th century were royal holdings as were the forests. Quality lumber was a closely controled commodity. You got the best that you could, used all that you could, and were probably happy just to get it.

That being said, The wood is now 140+ years old. The wood's tonal capacity more than makes up for any percieved shortcomings. And I say percieved shortcomings because the crowning capacity of the wood is still more than sufficient, as demonstrated in the photos.

It may be that our fetish for perfectly quartersawn lumber is just that: a fetish. a preferrence that is not really demanded of the enterprise.

A lot of old boards have less than quartersawn wood in them, and a lot of it seems to be used in the rear section of the board. In the back, under the plate, and so out of sight. Saving the clean stuff for where it can be seen? That would be human nature. Or it could be placed there so that the bass bridge would sit on a more compliant zone of the board.

The only board I ever saw with perfectly quartersawn wood throughout the board was from a Chickering square from the 1870s. We still have it, just for looking at.

Why one by one? Half the reason has to do with our use of hide glue. In the pictures you can see how the hide glue squeezes out onto the surface of the board. You can see how wet the surface gets from the clean up. We've never felt comfortable attatching another rib until the board has given that moisture up. We also like to keep the board at the working temperature. In the time it takes to glue the rib, the whole board cools, we wrap it up til everything is back to warm and dry. The other reason is that we just have'nt gotten around to it. Shameful, I know.

Future cracking. You are referring to the mortal fear of compression ridges? First, I think I must point out that all the literature is written about new wood. Old wood is qualitatively different. Rather than being weaker than new wood, it is actually a good bit stronger, particularly across the grain. Its hygroscopic movement may or may not be equal to that of new wood,( don't know, never used any), but its ability to absorb this pressure without damaging itself is greater. We just have'nt had any occurances of compression ridges. which is probably why we have had a tendancy to put maybe little too healthy a crown in the board. Too much crown has always seemed a better bet than too little, as the excess arch can be pressed out when mounting. This increases the compression in the panel and raises the impedance of the board as a whole. It also means that there will be more time before the natural shrinkage puts the panel into tension, and starts it into pulling on the ribs. In new wood, this might be a recipe for disaster. The old wood seems to take it without a problem.

Some thoughts on seasoning of wood. The whole purpose of seasoning wood is to make it stable, and its behavior predictable within a window of acceptable limits, so that it might be used as a reliable engineering material. Spruce is a conifer, and like all conifers it is a very wet wood. Both in terms of water and organic volitals. Excess water weight is easily lost to the air, this is drying, and that is all it is. Seasoning is what takes place after the water is lost. Seasoning is the stabilization of the resins in the wood, and that takes a while (seasons). In its first years, when the wood still has a lot of soft resins in it, the wood moves a great deal with the natural movement of water in and out of the cells. At the same time, the softness of the resins keep the wood's compression failure limit rather low. Consequently the wood has a strong capacity to expasnd and a weaker capacity to resist. With the seasons, the expansive tendancy lessens while the resistive potential increases. Like two lines on a graph, they converge. When the two lines meet, the wood is finally strong enough to resist its own strength. This would be the point where the wood could be safely used for predictable results. This is just traditional seasoning.

Where am I goiung with this? Well that process does not stop. It slows and slows, becomming glacial, but over a century has a cumulative effect. Accumulated shrinkage pulls the board flat or even concave. If that shrinkage is relieved, however, the panel once again has the capacity to expand and bend the ribs. And being stronger, it can do that without approaching the compressive fiber limit. I think that is why we have not had problems with compression ridges.

I agree, though, that we could probably dial back on the crown a bit. We have done some experiments with some boards from dead pianos, and it looks like we may be able to dispense with dished cauls altoghether and just press on a flat deck, go pure compression.

Thank you very much for your answers and the interesting background, Mr. Hair.

Best regards-

Originally Posted By: Craig Hair

Good evening,Its only part illusion. the grain is far from vertical. Actually much of the wood in this board seems less than ideal. There is a lot of grain runout in the planks. One board has a curve of about 2 inches in the grain from one end to the other.

Perhapse we are just spoiled when it comes to wood selection in America. The German city-states of the 19th century were royal holdings as were the forests. Quality lumber was a closely controled commodity. You got the best that you could, used all that you could, and were probably happy just to get it.

That being said, The wood is now 140+ years old. The wood's tonal capacity more than makes up for any percieved shortcomings. And I say percieved shortcomings because the crowning capacity of the wood is still more than sufficient, as demonstrated in the photos.

It may be that our fetish for perfectly quartersawn lumber is just that: a fetish. a preferrence that is not really demanded of the enterprise.

A lot of old boards have less than quartersawn wood in them, and a lot of it seems to be used in the rear section of the board. In the back, under the plate, and so out of sight. Saving the clean stuff for where it can be seen? That would be human nature. Or it could be placed there so that the bass bridge would sit on a more compliant zone of the board.

The only board I ever saw with perfectly quartersawn wood throughout the board was from a Chickering square from the 1870s. We still have it, just for looking at.

Hello Craig,A while back, you stated that you were going to try and revive the original strings. I was wondering if you have done so, and if so, did they they respond? Could you expound on the process?Thanks,Carl

Kyle,thanks, we appreciate the compliment. This certainly is an interesting piano. The piano is very modern for its day, but the bass bridge is still unlike anything else I've seen. Its like three bridges in one. One thing I can say is that this is the lowest mass bass bridge Ive ever seen. The closest is the bridge-on-the-bridge construction in the Knabes from the 1890s. (In passing, those knabes also used a rib-crowned suspension with a contoured rim. Earliest I know of.)

We do sand the caps some to make a smoother surface, but I don't think there is as much material removed as it appears. Perhaps half a mm, if that.

If the board were still mounted to the rim then a mm lost in bridge height could mean a mm lost in bearing. But this board is out and already has more than sufficient crown. So I don't think there will be any problem accomodating a small dimensional change; considering also that the tennor bridge will be similarly treated.

For now the bridge just has some shellac on it to keep it clean. they will later be alcohol cleaned and french polished. The cap face is finished with a 220 one direction sanding, colored with Higgins's Black Magic(high quality india ink), then burnished with graphite with a leather covered wooden block.